Allow users to specify whether to use cabal's multi-repl feature

We add an option to `Config` that allows clients to specify how HLS
should load components.

The three options are:

* SessionLoadSingleComponent: Always load only a single component
    when a new component is discovered.
* SessionLoadMultipleComponents: Always allow the cradle to load
    multiple components at once. This might not be always possible,
    e.g., if the tool doesn't support multiple components loading.
    The cradle can decide how to handle these situations.
* SessionAuto: Leave the decision to the individual cradle type.
    Some cradles have good support for loading multiple components,
    while others do not.
    So use multiple components loading for tools, such as cabal,
    and force single component loading for tools that do not support
    multiple components, such as stack.

Author: fendor

cabal.project

@@ -42,3 +42,8 @@ constraints:
   -- We want to be able to benefit from the performance optimisations
   -- in the future, thus: TODO: remove this flag.
   bitvec -simd
+
+source-repository-package
+    type: git
+    location: https://github.com/fendor/hie-bios
+    tag: 10afd5b50475b7f8877296cd65614a1a72253941